A known controller for a web of material, in this case a metal strip, which regulates and controls the variations in the lateral position of a running material web comprises a regulated stretch of the material web having a guide member, especially a guide roller, at one end and a controllable guiding mechanism able to angularly divert the material web passing through the regulated stretch.
The control of the guiding mechanism depends on the angular displacement of the web control roller occuring in a guided segment of the material web adjacent the regulated stretch.
The guided segment of the material web passing over the guide member is deflected approximately at a right angle to the running direction of the regulated stretch. At least one video camera is provided for observing the edge motion and course of the material web: an electrical image signal from this camera is convertable by a computer into a controlling command for the guide mechanism and has an optical axis oriented approximately parallel to the regulated stretch of the material web.
This web-position controller is described in literature reference "VDI-Nachrichten, June, 1980, Nr. 23, Seite 16". In this known web-position controller the video camera is mounted downstream from the guide member. The guide member is formed as a guide roller and acts as a controlling roller for the course of the conveyor belt. The length of the regulated stretch and the viewing distance of the video camera to the guide member add to one another and lead to correspondingly larger structural measurements.
Each material web edge has its own camera. A light source illuminating the material web edge in reflected light or transmitted light can serve to light up the image field of the video camera. The electronic signal analyzer forms from both camera images an analog voltage corresponding to the material web position. The web-position controller opens a servovalve proportionally to the deviation of the material web from the proper line, which activates an adjusting cylinder causing a controlled pivoting of the controlling roller.
This pivoting leads to a lateral displacement of the material web until the belt is properly centered on the guide members.